How do you use Linux permission and ownership commands and utilities such as chmod, chown, and umask?

Linux provides powerful tools for user access control. Commands like chmod, chown, and umask offer incredible control over permissions and ownership. Linux outshines other OSs in this aspect. With these native tools, you can configure the entire security system without relying on third-party apps. It's a game-changer for fine-tuning access levels and restrictions.

?? chmod: Change file permissions. Use 'chmod' followed by a 3-digit code (e.g., 644) to set permissions (read, write, execute) for owner, group, and others. ?? chown: Change file ownership. Employ 'chown' to alter file ownership (user and group) with 'sudo chown user:group file'. ?? umask: Set default permissions. 'Umask' sets default permission masks for new files and directories. ?? Example: chmod 755 file grants read/write/execute for the owner, and read/execute for group/others. ??? Ensure safety: Be cautious when changing permissions and ownership to prevent system instability. ?? Reference 'man' pages: Use 'man chmod', 'man chown', and 'man umask' for detailed info.

chmod: To set the permission levels on a file or directory chown : To set the ownership of a file or directory umask: To set default permissions for newly created files or directory. While the first 2 commands have to be run as and when needed. The third one can be set as a default setting .

The 3 permissions (read, write, execute) are coded bitwise (r * 2^2 + w * 2^1 + x * 2^0), meaning a rwx condition of YYN would be 1 * 4 + 1 * 2 + 0 * 1 = 6. There are 3 such permission groups: for the user, for the group and for others. (For example: rwx r-x r-- or 754)

chmod and chown are use for managing permissions of files and dirs in linux OS. e.g. $chmod 755 awesome_file it means the "awesome_file" will have -rwxr-xr-x permissions In this rwx represents r = 4, w=2,x=1 "-" defines the type of object "awesome_file" that is file. (first character is "d" then it is a directory. "rwx" represents owner's permission that is 4+2+1 = 7 "r-x" represents group's permission that is 4+0+1 = 5 last "r-x" represents other's permission that is 4+0+1 = 5 Chown is used to change the ownership of a file. $chown <ownername>:<groupname> filename Umask can be 022 or 002. It is used in core skeleton files of linux for permissions calculations that the permission is being set for files/dirs for Root or local user

Remember that you should use the chmod command with caution, especially when changing permissions on system files or directories, to avoid unintended consequences and potential security risks.

chmod command is used to change the permissions of a file or directory, it can be used to add, remove or modify the permission for the owner or group

Usually you can use chmod command with +x , 777, ... Parameter for change permission and ownership to run a task and you able to make a file executable.

System Admin has to grant permission as per approval, he must restrict write acces to users for the Linux file system or files, try to grant them read access most of the time as required, and only allow execute access to authorised one.

You should be careful when using the chmod, because the permission you are giving is a system vulnerability. Access Control Lists (ACLs): As mentioned earlier, ACLs provide finer-grained control over file and directory permissions. You can use them to specify access for specific users or groups. AppArmor and SELinux: These are Mandatory Access Control (MAC) systems that provide an additional layer of security. They can restrict the actions of individual processes and limit their access to files and directories. File Attributes: Use file attributes like the immutable attribute (set with chattr) to prevent files from being modified or deleted, even by the superuser.

We utilized the 'chown' command to enhance data security and access control for sensitive files within a shared directory. By changing ownership and group assignments, and using the recursive option, we ensured that only authorized users had access, aligning with compliance standards.

Remember that you typically need superuser (root) privileges to change ownership of files that you do not own. Be cautious when using the chown command, as changing ownership of system files or directories can impact the functioning of your system.

chown command is used to change the owner and group of a file or directory, allows youto transfer ownership to another user or group

Make sure to make backup of file modes or permissions below doing a recursive chown on a production server and/or folders. You can use below command to do it. $ ls -lR /opt/oracle > /tmp/opt_oracle_permissions.bkp

Keep in mind that the umask is a protective measure that restricts permissions by default, and it's often used to enhance security and privacy. However, it can be adjusted to meet the specific needs of your environment.

umask command is used to set the default permissions for newly created files and directories. Specifies which permissions are not allowed by default

This might be a little off-topic, but very often after performing a filesystem restore there might be permission issues with applications. It is best to make note of how the permissions should look like prior to restoring the data and double-checking after the restore.

Before you change ANYTHING using chown, chmod, or umask, take a moment to try group users who need specific access to a resource(s). Those resources commonly are those that cross organizations, so, for example, engineering and project management might share a directory so that directory and only that directory should be in a new group such as "shared-eng-projmgt". That group name, and a new GID, go into the file /etc/groups. There is an additional problem: most modern corporations used to have "silos" where each organization had its own set of UIDs and GIDs. As part of breaking down silos, there has to be corporate wide agreement on UIDs and GIDs. This is hard, but it will be worth it.

Before you start playing around with special permissions (SUID/SGID) (rwsr_x_r_x) (rwx_rwsr_x) please take a moment to think if you really need to apply them on the specific file/directory. This is a surefire way to compromise your system's security.

Make sure to make backup of file modes or permissions below doing a recursive chmod/chown on a production server and/or folders. You can pattern below command to do it. $ ls -lR /opt/oracle > /tmp/opt_oracle_permissions.bkp

Note that the permission system doesn't only allow control over who can access what directories or files, but also can be used by programs/services to determine if there is any issue. For example: ssh server will not accept a authorized_keys file as valid unless the whole path is not others writable and ownership and access is set to (only) the user that is authenicated for. So if a program isn't working consider that not only can the permissions be to narrow, but also too wide

The chown command in linux OS is used to change the ownership of files and directories. It allows you to change both the user and group ownership of a file or directory. The command is typically used by superusers (e.g., root) or users with appropriate permissions to manage file ownership.

Although it feels like the quick and easy fix, always evaluate if setting rights to 777 is the correct way: most often it is not. Linux/unix has a comprehensive file access and user management framework, extended with security tools such as sudo and chroot. Using group rights and memberships, umask, chown (including extended settings such as sticky bit and such) allows for many secure solutions.